package com.twmacinta.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Fast implementation of RSA's MD5 hash generator in Java JDK Beta-2 or higher.
 * <p>
 * Originally written by Santeri Paavolainen, Helsinki Finland 1996.<br>
 * (c) Santeri Paavolainen, Helsinki Finland 1996<br>
 * Many changes Copyright (c) 2002 - 2010 Timothy W Macinta<br>
 * <p>
 * This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * <p>
 * See http://www.twmacinta.com/myjava/fast_md5.php for more information on this file and the related files.
 * <p>
 * This was originally a rather straight re-implementation of the reference implementation given in RFC1321 by RSA. It passes the
 * MD5 test suite as defined in RFC1321.
 * <p>
 * Many optimizations made by Timothy W Macinta. Reduced time to checksum a test file in Java alone to roughly half the time taken
 * compared with java.security.MessageDigest (within an intepretter). Also added an optional native method to reduce the time even
 * further. See http://www.twmacinta.com/myjava/fast_md5.php for further information on the time improvements achieved.
 * <p>
 * Some bug fixes also made by Timothy W Macinta.
 * <p>
 * Please note: I (Timothy Macinta) have put this code in the com.twmacinta.util package only because it came without a package. I
 * was not the the original author of the code, although I did optimize it (substantially) and fix some bugs.
 * <p>
 * This Java class has been derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm and its reference
 * implementation.
 * <p>
 * This class will attempt to use a native method to quickly compute checksums when the appropriate native library is available.
 * On Linux, this library should be named "MD5.so" and on Windows it should be named "MD5.dll". The code will attempt to locate
 * the library in the following locations in the order given:
 * 
 * <ol>
 * <li>The path specified by the system property "com.twmacinta.util.MD5.NATIVE_LIB_FILE" (be sure to include "MD5.so", "MD5.dll",
 * or "MD5.jnilib" as appropriate at the end of the path).
 * <li>A platform specific directory beneath the "lib/arch/" directory. For example, On Windows for 32 bit x86 architectures, this
 * is "lib/arch/win32_x86/".
 * <li>Within the "lib/" directory.
 * <li>Within the current directory.
 * </ol>
 * 
 * <p>
 * If the library is not found, the code will fall back to the default (slower) Java code.
 * <p>
 * As a side effect of having the code search for the native library, SecurityExceptions might be thrown on JVMs that have a
 * restrictive SecurityManager. The initialization code attempts to silently discard these exceptions and continue, but many
 * SecurityManagers will attempt to notify the user directly of all SecurityExceptions thrown. Consequently, the code has
 * provisions for skipping the search for the native library. Any of these provisions may be used to skip the search as long as
 * they are performed <i>before</i> the first instance of a com.twmacinta.util.MD5 object is constructed (note that the
 * convenience stream objects will implicitly create an MD5 object).
 * <p>
 * The first option is to set the system property "com.twmacinta.util.MD5.NO_NATIVE_LIB" to "true" or "1". Unfortunately,
 * SecurityManagers may also choose to disallow system property setting, so this won't be of use in all cases.
 * <p>
 * The second option is to call com.twmacinta.util.MD5.initNativeLibrary(true) before any MD5 objects are constructed.
 * 
 * @author Santeri Paavolainen &lt;sjpaavol@cc.helsinki.fi&gt;
 * @author Timothy W Macinta (twm@alum.mit.edu) (optimizations and bug fixes)
 */

public class MD5 {

	/**
	 * MD5 state
	 **/
	MD5State state;

	/**
	 * If Final() has been called, finals is set to the current finals state. Any Update() causes this to be set to null.
	 **/
	MD5State finals;

	/**
	 * Padding for Final()
	 **/
	static byte padding[] = { (byte) 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

	private static boolean native_lib_loaded = false;
	private static boolean native_lib_init_pending = true;

	/**
	 * Initialize MD5 internal state (object can be reused just by calling Init() after every Final()
	 **/
	public synchronized void Init() {
		state = new MD5State();
		finals = null;
	}

	/**
	 * Class constructor
	 **/
	public MD5() {
		if (native_lib_init_pending)
			_initNativeLibrary();
		this.Init();
	}

	/**
	 * Initialize class, and update hash with ob.toString()
	 * 
	 * @param ob
	 *            Object, ob.toString() is used to update hash after initialization
	 **/
	public MD5(Object ob) {
		this();
		Update(ob.toString());
	}

	private void Decode(byte buffer[], int shift, int[] out) {
		/*
		 * len += shift; for (int i = 0; shift < len; i++, shift += 4) { out[i] = ((int) (buffer[shift] & 0xff)) | (((int)
		 * (buffer[shift + 1] & 0xff)) << 8) | (((int) (buffer[shift + 2] & 0xff)) << 16) | (((int) buffer[shift + 3]) << 24); }
		 */

		// unrolled loop (original loop shown above)

		out[0] = ((int) (buffer[shift] & 0xff)) | (((int) (buffer[shift + 1] & 0xff)) << 8)
				| (((int) (buffer[shift + 2] & 0xff)) << 16) | (((int) buffer[shift + 3]) << 24);
		out[1] = ((int) (buffer[shift + 4] & 0xff)) | (((int) (buffer[shift + 5] & 0xff)) << 8)
				| (((int) (buffer[shift + 6] & 0xff)) << 16) | (((int) buffer[shift + 7]) << 24);
		out[2] = ((int) (buffer[shift + 8] & 0xff)) | (((int) (buffer[shift + 9] & 0xff)) << 8)
				| (((int) (buffer[shift + 10] & 0xff)) << 16) | (((int) buffer[shift + 11]) << 24);
		out[3] = ((int) (buffer[shift + 12] & 0xff)) | (((int) (buffer[shift + 13] & 0xff)) << 8)
				| (((int) (buffer[shift + 14] & 0xff)) << 16) | (((int) buffer[shift + 15]) << 24);
		out[4] = ((int) (buffer[shift + 16] & 0xff)) | (((int) (buffer[shift + 17] & 0xff)) << 8)
				| (((int) (buffer[shift + 18] & 0xff)) << 16) | (((int) buffer[shift + 19]) << 24);
		out[5] = ((int) (buffer[shift + 20] & 0xff)) | (((int) (buffer[shift + 21] & 0xff)) << 8)
				| (((int) (buffer[shift + 22] & 0xff)) << 16) | (((int) buffer[shift + 23]) << 24);
		out[6] = ((int) (buffer[shift + 24] & 0xff)) | (((int) (buffer[shift + 25] & 0xff)) << 8)
				| (((int) (buffer[shift + 26] & 0xff)) << 16) | (((int) buffer[shift + 27]) << 24);
		out[7] = ((int) (buffer[shift + 28] & 0xff)) | (((int) (buffer[shift + 29] & 0xff)) << 8)
				| (((int) (buffer[shift + 30] & 0xff)) << 16) | (((int) buffer[shift + 31]) << 24);
		out[8] = ((int) (buffer[shift + 32] & 0xff)) | (((int) (buffer[shift + 33] & 0xff)) << 8)
				| (((int) (buffer[shift + 34] & 0xff)) << 16) | (((int) buffer[shift + 35]) << 24);
		out[9] = ((int) (buffer[shift + 36] & 0xff)) | (((int) (buffer[shift + 37] & 0xff)) << 8)
				| (((int) (buffer[shift + 38] & 0xff)) << 16) | (((int) buffer[shift + 39]) << 24);
		out[10] = ((int) (buffer[shift + 40] & 0xff)) | (((int) (buffer[shift + 41] & 0xff)) << 8)
				| (((int) (buffer[shift + 42] & 0xff)) << 16) | (((int) buffer[shift + 43]) << 24);
		out[11] = ((int) (buffer[shift + 44] & 0xff)) | (((int) (buffer[shift + 45] & 0xff)) << 8)
				| (((int) (buffer[shift + 46] & 0xff)) << 16) | (((int) buffer[shift + 47]) << 24);
		out[12] = ((int) (buffer[shift + 48] & 0xff)) | (((int) (buffer[shift + 49] & 0xff)) << 8)
				| (((int) (buffer[shift + 50] & 0xff)) << 16) | (((int) buffer[shift + 51]) << 24);
		out[13] = ((int) (buffer[shift + 52] & 0xff)) | (((int) (buffer[shift + 53] & 0xff)) << 8)
				| (((int) (buffer[shift + 54] & 0xff)) << 16) | (((int) buffer[shift + 55]) << 24);
		out[14] = ((int) (buffer[shift + 56] & 0xff)) | (((int) (buffer[shift + 57] & 0xff)) << 8)
				| (((int) (buffer[shift + 58] & 0xff)) << 16) | (((int) buffer[shift + 59]) << 24);
		out[15] = ((int) (buffer[shift + 60] & 0xff)) | (((int) (buffer[shift + 61] & 0xff)) << 8)
				| (((int) (buffer[shift + 62] & 0xff)) << 16) | (((int) buffer[shift + 63]) << 24);
	}

	private native void Transform_native(int[] state, byte buffer[], int shift, int length);

	private void Transform(MD5State state, byte buffer[], int shift, int[] decode_buf) {
		int a = state.state[0], b = state.state[1], c = state.state[2], d = state.state[3], x[] = decode_buf;

		Decode(buffer, shift, decode_buf);

		/* Round 1 */
		a += ((b & c) | (~b & d)) + x[0] + 0xd76aa478; /* 1 */
		a = ((a << 7) | (a >>> 25)) + b;
		d += ((a & b) | (~a & c)) + x[1] + 0xe8c7b756; /* 2 */
		d = ((d << 12) | (d >>> 20)) + a;
		c += ((d & a) | (~d & b)) + x[2] + 0x242070db; /* 3 */
		c = ((c << 17) | (c >>> 15)) + d;
		b += ((c & d) | (~c & a)) + x[3] + 0xc1bdceee; /* 4 */
		b = ((b << 22) | (b >>> 10)) + c;

		a += ((b & c) | (~b & d)) + x[4] + 0xf57c0faf; /* 5 */
		a = ((a << 7) | (a >>> 25)) + b;
		d += ((a & b) | (~a & c)) + x[5] + 0x4787c62a; /* 6 */
		d = ((d << 12) | (d >>> 20)) + a;
		c += ((d & a) | (~d & b)) + x[6] + 0xa8304613; /* 7 */
		c = ((c << 17) | (c >>> 15)) + d;
		b += ((c & d) | (~c & a)) + x[7] + 0xfd469501; /* 8 */
		b = ((b << 22) | (b >>> 10)) + c;

		a += ((b & c) | (~b & d)) + x[8] + 0x698098d8; /* 9 */
		a = ((a << 7) | (a >>> 25)) + b;
		d += ((a & b) | (~a & c)) + x[9] + 0x8b44f7af; /* 10 */
		d = ((d << 12) | (d >>> 20)) + a;
		c += ((d & a) | (~d & b)) + x[10] + 0xffff5bb1; /* 11 */
		c = ((c << 17) | (c >>> 15)) + d;
		b += ((c & d) | (~c & a)) + x[11] + 0x895cd7be; /* 12 */
		b = ((b << 22) | (b >>> 10)) + c;

		a += ((b & c) | (~b & d)) + x[12] + 0x6b901122; /* 13 */
		a = ((a << 7) | (a >>> 25)) + b;
		d += ((a & b) | (~a & c)) + x[13] + 0xfd987193; /* 14 */
		d = ((d << 12) | (d >>> 20)) + a;
		c += ((d & a) | (~d & b)) + x[14] + 0xa679438e; /* 15 */
		c = ((c << 17) | (c >>> 15)) + d;
		b += ((c & d) | (~c & a)) + x[15] + 0x49b40821; /* 16 */
		b = ((b << 22) | (b >>> 10)) + c;

		/* Round 2 */
		a += ((b & d) | (c & ~d)) + x[1] + 0xf61e2562; /* 17 */
		a = ((a << 5) | (a >>> 27)) + b;
		d += ((a & c) | (b & ~c)) + x[6] + 0xc040b340; /* 18 */
		d = ((d << 9) | (d >>> 23)) + a;
		c += ((d & b) | (a & ~b)) + x[11] + 0x265e5a51; /* 19 */
		c = ((c << 14) | (c >>> 18)) + d;
		b += ((c & a) | (d & ~a)) + x[0] + 0xe9b6c7aa; /* 20 */
		b = ((b << 20) | (b >>> 12)) + c;

		a += ((b & d) | (c & ~d)) + x[5] + 0xd62f105d; /* 21 */
		a = ((a << 5) | (a >>> 27)) + b;
		d += ((a & c) | (b & ~c)) + x[10] + 0x02441453; /* 22 */
		d = ((d << 9) | (d >>> 23)) + a;
		c += ((d & b) | (a & ~b)) + x[15] + 0xd8a1e681; /* 23 */
		c = ((c << 14) | (c >>> 18)) + d;
		b += ((c & a) | (d & ~a)) + x[4] + 0xe7d3fbc8; /* 24 */
		b = ((b << 20) | (b >>> 12)) + c;

		a += ((b & d) | (c & ~d)) + x[9] + 0x21e1cde6; /* 25 */
		a = ((a << 5) | (a >>> 27)) + b;
		d += ((a & c) | (b & ~c)) + x[14] + 0xc33707d6; /* 26 */
		d = ((d << 9) | (d >>> 23)) + a;
		c += ((d & b) | (a & ~b)) + x[3] + 0xf4d50d87; /* 27 */
		c = ((c << 14) | (c >>> 18)) + d;
		b += ((c & a) | (d & ~a)) + x[8] + 0x455a14ed; /* 28 */
		b = ((b << 20) | (b >>> 12)) + c;

		a += ((b & d) | (c & ~d)) + x[13] + 0xa9e3e905; /* 29 */
		a = ((a << 5) | (a >>> 27)) + b;
		d += ((a & c) | (b & ~c)) + x[2] + 0xfcefa3f8; /* 30 */
		d = ((d << 9) | (d >>> 23)) + a;
		c += ((d & b) | (a & ~b)) + x[7] + 0x676f02d9; /* 31 */
		c = ((c << 14) | (c >>> 18)) + d;
		b += ((c & a) | (d & ~a)) + x[12] + 0x8d2a4c8a; /* 32 */
		b = ((b << 20) | (b >>> 12)) + c;

		/* Round 3 */
		a += (b ^ c ^ d) + x[5] + 0xfffa3942; /* 33 */
		a = ((a << 4) | (a >>> 28)) + b;
		d += (a ^ b ^ c) + x[8] + 0x8771f681; /* 34 */
		d = ((d << 11) | (d >>> 21)) + a;
		c += (d ^ a ^ b) + x[11] + 0x6d9d6122; /* 35 */
		c = ((c << 16) | (c >>> 16)) + d;
		b += (c ^ d ^ a) + x[14] + 0xfde5380c; /* 36 */
		b = ((b << 23) | (b >>> 9)) + c;

		a += (b ^ c ^ d) + x[1] + 0xa4beea44; /* 37 */
		a = ((a << 4) | (a >>> 28)) + b;
		d += (a ^ b ^ c) + x[4] + 0x4bdecfa9; /* 38 */
		d = ((d << 11) | (d >>> 21)) + a;
		c += (d ^ a ^ b) + x[7] + 0xf6bb4b60; /* 39 */
		c = ((c << 16) | (c >>> 16)) + d;
		b += (c ^ d ^ a) + x[10] + 0xbebfbc70; /* 40 */
		b = ((b << 23) | (b >>> 9)) + c;

		a += (b ^ c ^ d) + x[13] + 0x289b7ec6; /* 41 */
		a = ((a << 4) | (a >>> 28)) + b;
		d += (a ^ b ^ c) + x[0] + 0xeaa127fa; /* 42 */
		d = ((d << 11) | (d >>> 21)) + a;
		c += (d ^ a ^ b) + x[3] + 0xd4ef3085; /* 43 */
		c = ((c << 16) | (c >>> 16)) + d;
		b += (c ^ d ^ a) + x[6] + 0x04881d05; /* 44 */
		b = ((b << 23) | (b >>> 9)) + c;

		a += (b ^ c ^ d) + x[9] + 0xd9d4d039; /* 33 */
		a = ((a << 4) | (a >>> 28)) + b;
		d += (a ^ b ^ c) + x[12] + 0xe6db99e5; /* 34 */
		d = ((d << 11) | (d >>> 21)) + a;
		c += (d ^ a ^ b) + x[15] + 0x1fa27cf8; /* 35 */
		c = ((c << 16) | (c >>> 16)) + d;
		b += (c ^ d ^ a) + x[2] + 0xc4ac5665; /* 36 */
		b = ((b << 23) | (b >>> 9)) + c;

		/* Round 4 */
		a += (c ^ (b | ~d)) + x[0] + 0xf4292244; /* 49 */
		a = ((a << 6) | (a >>> 26)) + b;
		d += (b ^ (a | ~c)) + x[7] + 0x432aff97; /* 50 */
		d = ((d << 10) | (d >>> 22)) + a;
		c += (a ^ (d | ~b)) + x[14] + 0xab9423a7; /* 51 */
		c = ((c << 15) | (c >>> 17)) + d;
		b += (d ^ (c | ~a)) + x[5] + 0xfc93a039; /* 52 */
		b = ((b << 21) | (b >>> 11)) + c;

		a += (c ^ (b | ~d)) + x[12] + 0x655b59c3; /* 53 */
		a = ((a << 6) | (a >>> 26)) + b;
		d += (b ^ (a | ~c)) + x[3] + 0x8f0ccc92; /* 54 */
		d = ((d << 10) | (d >>> 22)) + a;
		c += (a ^ (d | ~b)) + x[10] + 0xffeff47d; /* 55 */
		c = ((c << 15) | (c >>> 17)) + d;
		b += (d ^ (c | ~a)) + x[1] + 0x85845dd1; /* 56 */
		b = ((b << 21) | (b >>> 11)) + c;

		a += (c ^ (b | ~d)) + x[8] + 0x6fa87e4f; /* 57 */
		a = ((a << 6) | (a >>> 26)) + b;
		d += (b ^ (a | ~c)) + x[15] + 0xfe2ce6e0; /* 58 */
		d = ((d << 10) | (d >>> 22)) + a;
		c += (a ^ (d | ~b)) + x[6] + 0xa3014314; /* 59 */
		c = ((c << 15) | (c >>> 17)) + d;
		b += (d ^ (c | ~a)) + x[13] + 0x4e0811a1; /* 60 */
		b = ((b << 21) | (b >>> 11)) + c;

		a += (c ^ (b | ~d)) + x[4] + 0xf7537e82; /* 61 */
		a = ((a << 6) | (a >>> 26)) + b;
		d += (b ^ (a | ~c)) + x[11] + 0xbd3af235; /* 62 */
		d = ((d << 10) | (d >>> 22)) + a;
		c += (a ^ (d | ~b)) + x[2] + 0x2ad7d2bb; /* 63 */
		c = ((c << 15) | (c >>> 17)) + d;
		b += (d ^ (c | ~a)) + x[9] + 0xeb86d391; /* 64 */
		b = ((b << 21) | (b >>> 11)) + c;

		state.state[0] += a;
		state.state[1] += b;
		state.state[2] += c;
		state.state[3] += d;
	}

	/**
	 * Updates hash with the bytebuffer given (using at maximum length bytes from that buffer)
	 * 
	 * @param stat
	 *            Which state is updated
	 * @param buffer
	 *            Array of bytes to be hashed
	 * @param offset
	 *            Offset to buffer array
	 * @param length
	 *            Use at maximum `length' bytes (absolute maximum is buffer.length)
	 */
	public void Update(MD5State stat, byte buffer[], int offset, int length) {
		int index, partlen, i, start;
		finals = null;

		/* Length can be told to be shorter, but not inter */
		if ((length - offset) > buffer.length)
			length = buffer.length - offset;

		/* compute number of bytes mod 64 */

		index = (int) (stat.count & 0x3f);
		stat.count += length;

		partlen = 64 - index;

		if (length >= partlen) {

			// update state (using native method) to reflect input

			if (native_lib_loaded) {
				if (partlen == 64) {
					partlen = 0;
				} else {
					for (i = 0; i < partlen; i++)
						stat.buffer[i + index] = buffer[i + offset];
					Transform_native(stat.state, stat.buffer, 0, 64);
				}
				i = partlen + ((length - partlen) / 64) * 64;

				// break into chunks to guard against stack overflow in JNI

				int transformLength = length - partlen;
				int transformOffset = partlen + offset;
				final int MAX_LENGTH = 65536; // prevent stack overflow in JNI
				while (true) {
					if (transformLength > MAX_LENGTH) {
						Transform_native(stat.state, buffer, transformOffset, MAX_LENGTH);
						transformLength -= MAX_LENGTH;
						transformOffset += MAX_LENGTH;
					} else {
						Transform_native(stat.state, buffer, transformOffset, transformLength);
						break;
					}
				}
			}

			// update state (using only Java) to reflect input

			else {
				int[] decode_buf = new int[16];
				if (partlen == 64) {
					partlen = 0;
				} else {
					for (i = 0; i < partlen; i++)
						stat.buffer[i + index] = buffer[i + offset];
					Transform(stat, stat.buffer, 0, decode_buf);
				}
				for (i = partlen; (i + 63) < length; i += 64) {
					Transform(stat, buffer, i + offset, decode_buf);
				}
			}
			index = 0;
		} else {
			i = 0;
		}

		/* buffer remaining input */
		if (i < length) {
			start = i;
			for (; i < length; i++) {
				stat.buffer[index + i - start] = buffer[i + offset];
			}
		}
	}

	/*
	 * Update()s for other datatypes than byte[] also. Update(byte[], int) is only the main driver.
	 */

	/**
	 * Plain update, updates this object
	 **/
	public void Update(byte buffer[], int offset, int length) {
		Update(this.state, buffer, offset, length);
	}

	public void Update(byte buffer[], int length) {
		Update(this.state, buffer, 0, length);
	}

	/**
	 * Updates hash with given array of bytes
	 * 
	 * @param buffer
	 *            Array of bytes to use for updating the hash
	 **/
	public void Update(byte buffer[]) {
		Update(buffer, 0, buffer.length);
	}

	/**
	 * Updates hash with a single byte
	 * 
	 * @param b
	 *            Single byte to update the hash
	 **/
	public void Update(byte b) {
		byte buffer[] = new byte[1];
		buffer[0] = b;

		Update(buffer, 1);
	}

	/**
	 * Update buffer with given string. Note that because the version of the s.getBytes() method without parameters is used to
	 * convert the string to a byte array, the results of this method may be different on different platforms. The s.getBytes()
	 * method converts the string into a byte array using the current platform's default character set and may therefore have
	 * different results on platforms with different default character sets. If a version that works consistently across platforms
	 * with different default character sets is desired, use the overloaded version of the Update() method which takes a string
	 * and a character encoding.
	 * 
	 * @param s
	 *            String to be update to hash (is used as s.getBytes())
	 **/
	public void Update(String s) {
		byte chars[] = s.getBytes();
		Update(chars, chars.length);
	}

	/**
	 * Update buffer with given string using the given encoding. If the given encoding is null, the encoding "ISO8859_1" is used.
	 * 
	 * @param s
	 *            String to be update to hash (is used as s.getBytes(charset_name))
	 * @param charset_name
	 *            The character set to use to convert s to a byte array, or null if the "ISO8859_1" character set is desired.
	 * @exception java.io.UnsupportedEncodingException
	 *                If the named charset is not supported.
	 **/
	public void Update(String s, String charset_name) throws java.io.UnsupportedEncodingException {
		if (charset_name == null)
			charset_name = "ISO8859_1";
		byte chars[] = s.getBytes(charset_name);
		Update(chars, chars.length);
	}

	/**
	 * Update buffer with a single integer (only &amp; 0xff part is used, as a byte)
	 * 
	 * @param i
	 *            Integer value, which is then converted to byte as i &amp; 0xff
	 **/
	public void Update(int i) {
		Update((byte) (i & 0xff));
	}

	private byte[] Encode(int input[], int len) {
		int i, j;
		byte out[];

		out = new byte[len];

		for (i = j = 0; j < len; i++, j += 4) {
			out[j] = (byte) (input[i] & 0xff);
			out[j + 1] = (byte) ((input[i] >>> 8) & 0xff);
			out[j + 2] = (byte) ((input[i] >>> 16) & 0xff);
			out[j + 3] = (byte) ((input[i] >>> 24) & 0xff);
		}

		return out;
	}

	/**
	 * Returns array of bytes (16 bytes) representing hash as of the current state of this object. Note: getting a hash does not
	 * invalidate the hash object, it only creates a copy of the real state which is finalized.
	 * 
	 * @return Array of 16 bytes, the hash of all updated bytes
	 **/
	public synchronized byte[] Final() {
		byte bits[];
		int index, padlen;
		MD5State fin;

		if (finals == null) {
			fin = new MD5State(state);

			int[] count_ints = { (int) (fin.count << 3), (int) (fin.count >> 29) };
			bits = Encode(count_ints, 8);

			index = (int) (fin.count & 0x3f);
			padlen = (index < 56) ? (56 - index) : (120 - index);

			Update(fin, padding, 0, padlen);
			Update(fin, bits, 0, 8);

			/* Update() sets finals to null */
			finals = fin;
		}

		return Encode(finals.state, 16);
	}

	private static final char[] HEX_CHARS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', };

	/**
	 * Turns array of bytes into string representing each byte as unsigned hex number.
	 * 
	 * @param hash
	 *            Array of bytes to convert to hex-string
	 * @return Generated hex string
	 */
	public static String asHex(byte hash[]) {
		char buf[] = new char[hash.length * 2];
		for (int i = 0, x = 0; i < hash.length; i++) {
			buf[x++] = HEX_CHARS[(hash[i] >>> 4) & 0xf];
			buf[x++] = HEX_CHARS[hash[i] & 0xf];
		}
		return new String(buf);
	}

	/**
	 * Returns 32-character hex representation of this objects hash
	 * 
	 * @return String of this object's hash
	 */
	public String asHex() {
		return asHex(this.Final());
	}

	/**
	 * Convenience method for initNativeLibrary(false).
	 **/
	public static synchronized final boolean initNativeLibrary() {
		return initNativeLibrary(false);
	}

	/**
	 * Attempts to initialize native library support. If 'disallow_lib_loading' is true, will indicate that the native library
	 * should not be loaded now or in the future. If native library support has been previously loaded or disabled, this method
	 * has no effect.
	 * 
	 * @return true iff native library support has been loaded
	 **/
	public static synchronized final boolean initNativeLibrary(boolean disallow_lib_loading) {
		if (disallow_lib_loading) {
			native_lib_init_pending = false;
		} else {
			_initNativeLibrary();
		}
		return native_lib_loaded;
	}

	private static synchronized final void _initNativeLibrary() {
		if (!native_lib_init_pending)
			return;
		native_lib_loaded = _loadNativeLibrary();
		native_lib_init_pending = false;
	}

	private static synchronized final boolean _loadNativeLibrary() {
		try {

			// don't try to load if the right property is set

			String prop = System.getProperty("com.twmacinta.util.MD5.NO_NATIVE_LIB");
			if (prop != null) {
				prop = prop.trim();
				if (prop.equalsIgnoreCase("true") || prop.equals("1"))
					return false;
			}

			// the library to load can be specified as a property

			File f;
			prop = System.getProperty("com.twmacinta.util.MD5.NATIVE_LIB_FILE");
			if (prop != null) {
				f = new File(prop);
				if (f.canRead()) {
					System.load(f.getAbsolutePath());
					return true;
				}
			}

			// determine the operating system and architecture

			String os_name = System.getProperty("os.name");
			String os_arch = System.getProperty("os.arch");
			if (os_name == null || os_arch == null)
				return false;
			os_name = os_name.toLowerCase();
			os_arch = os_arch.toLowerCase();

			// define settings which are OS arch architecture independent

			File arch_lib_path = null;
			String arch_libfile_suffix = null;

			// fill in settings for Linux on x86

			if (os_name.equals("linux")
					&& (os_arch.equals("x86") || os_arch.equals("i386") || os_arch.equals("i486") || os_arch.equals("i586") || os_arch
							.equals("i686"))) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "linux_x86");
				arch_libfile_suffix = ".so";
			}

			// fill in settings for Linux on amd64

			else if (os_name.equals("linux") && os_arch.equals("amd64")) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "linux_amd64");
				arch_libfile_suffix = ".so";
			}

			// fill in settings for Windows on x86

			else if (os_name.startsWith("windows ")
					&& (os_arch.equals("x86") || os_arch.equals("i386") || os_arch.equals("i486") || os_arch.equals("i586") || os_arch
							.equals("i686"))) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "win32_x86");
				arch_libfile_suffix = ".dll";
			}

			// fill in settings for Windows on amd64

			else if (os_name.startsWith("windows ") && os_arch.equals("amd64")) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "win_amd64");
				arch_libfile_suffix = ".dll";
			}

			// fill in settings for Mac OS X on PPC

			else if (os_name.startsWith("mac os x") && (os_arch.equals("ppc"))) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "darwin_ppc");
				arch_libfile_suffix = ".jnilib";
			}

			// fill in settings for Mac OS X on x86

			else if (os_name.startsWith("mac os x")
					&& (os_arch.equals("x86") || os_arch.equals("i386") || os_arch.equals("i486") || os_arch.equals("i586") || os_arch
							.equals("i686"))) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "darwin_x86");
				arch_libfile_suffix = ".jnilib";
			}

			// fill in settings for Mac OS X on x86_64

			else if (os_name.startsWith("mac os x") && os_arch.equals("x86_64")) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "darwin_x86_64");
				arch_libfile_suffix = ".jnilib";
			}

			// fill in settings for FreeBSD on x86

			else if (os_name.equals("freebsd")
					&& (os_arch.equals("x86") || os_arch.equals("i386") || os_arch.equals("i486") || os_arch.equals("i586") || os_arch
							.equals("i686"))) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "freebsd_x86");
				arch_libfile_suffix = ".so";
			}

			// fill in settings for FreeBSD on amd64

			else if (os_name.equals("freebsd") && os_arch.equals("amd64")) {
				arch_lib_path = new File(new File(new File("lib"), "arch"), "freebsd_amd64");
				arch_libfile_suffix = ".so";
			}

			// default to .so files with no architecture specific subdirectory

			else {
				arch_libfile_suffix = ".so";
			}

			// build the required filename

			String fname = "MD5" + arch_libfile_suffix;

			// try the architecture specific directory

			if (arch_lib_path != null) {
				f = new File(arch_lib_path, fname);
				if (f.canRead()) {
					System.load(f.getAbsolutePath());
					return true;
				}
			}

			// try the "lib" subdirectory

			f = new File(new File("lib"), fname);
			if (f.canRead()) {
				System.load(f.getAbsolutePath());
				return true;
			}

			// try the working directory

			f = new File(fname);
			if (f.canRead()) {
				System.load(f.getAbsolutePath());
				return true;
			}
		}

		// discard SecurityExceptions

		catch (SecurityException e) {
		}

		// Intercept UnsatisfiedLinkError since the code will still
		// work without the native method, but report it because it
		// indicates that the architecture detection and/or support
		// should be updated.

		catch (UnsatisfiedLinkError e) {
			e.printStackTrace();
		}

		// unable to load

		return false;
	}

	/**
	 * Calculates and returns the hash of the contents of the given file.
	 **/
	public static byte[] getHash(File f) throws IOException {
		if (!f.exists())
			throw new FileNotFoundException(f.toString());
		InputStream close_me = null;
		try {
			long buf_size = f.length();
			if (buf_size < 512)
				buf_size = 512;
			if (buf_size > 65536)
				buf_size = 65536;
			byte[] buf = new byte[(int) buf_size];
			MD5InputStream in = new MD5InputStream(new FileInputStream(f));
			close_me = in;
			while (in.read(buf) != -1)
				;
			in.close();
			return in.hash();
		} catch (IOException e) {
			if (close_me != null)
				try {
					close_me.close();
				} catch (Exception e2) {
				}
			throw e;
		}
	}

	/**
	 * @return true iff the first 16 bytes of both hash1 and hash2 are equal; both hash1 and hash2 are null; or either hash array
	 *         is less than 16 bytes in length and their lengths and all of their bytes are equal.
	 **/
	public static boolean hashesEqual(byte[] hash1, byte[] hash2) {
		if (hash1 == null)
			return hash2 == null;
		if (hash2 == null)
			return false;
		int targ = 16;
		if (hash1.length < 16) {
			if (hash2.length != hash1.length)
				return false;
			targ = hash1.length;
		} else if (hash2.length < 16) {
			return false;
		}
		for (int i = 0; i < targ; i++) {
			if (hash1[i] != hash2[i])
				return false;
		}
		return true;
	}

}
